Distributing valve for pneumatic tools



F. P. FORSS DISTRIBUTING VALVE FOR PNEUMATIC TooLs vFiled July 12, 1945l April 3, 1945.

INVENToR. /WH/af H Fons Patented Apr. 3, 1945 DISTRIBUTING VALVE FORPNEUMATIC rJIOOL Frithiof P. Forss, Aurora, Ill., assignor toIndependent Pneumatic Tool Company, Chicago, Ill., a corporation ofDelaware Application July 12, 1943, Serial No. 494,300

1 Claim. (Cl. 121-19) This invention relates to improvements incylindric distributing valves of the character disclosed in myco-pending application Serial No. 372.227, led December 30, 1940, nowPatent No. 2,334,403, granted November 16, 1943, for portable pneumatictools such as chipping hammers, riveting hammers, clay diggers or clayspades and the like.

The object and purpose of my present invention is to provide the valvemember of a construction which will absorb the shock of the repeatedimpacts of the valve member against the valve block in the rapid lateralshifting of the valve member in effecting reciprocation of the hammeringpiston and from the severe Vibrations set up from the :power blows ofthe piston on the chisel or other work element inserted into andsupported by the tool barrel to prevent cracking of the valve member.

In carrying out the object of my invention, I comprise the Valve memberof an outer cylindric shell of a heat treated alloy steel or other hardmetal to take a high grinding finish and to resist the wear on the valvemember in its operation Within the valve block and an inner portion orliner of aluminum or other soft material havin-g intimate contact or apressed fit within the outer shell to absorb the shocks to which thevalve member is subjected in the operation of the tool as abovementioned.

In the accompanying drawing:

Fig. 1 is a longitudinal sectional view with parts in elevation of aportable pneumatic chipping hammer equipped with a cylindricaldistributing valve member constructed in accordance with my invention,the Valve member. being shown in its shifted position for supplying airpressure to the rear end of the tool cylinder;

Fig. 2 is a Vertical sectional View taken on line 2-,2 of Fig. 1;

Fig. 3 is a horizontal sectional View taken on line 3-3 of Fig. 1;

Fig. 4 is an enlarged View of the assembled Valve member and valve blockremoved `from the tool and in section on line 4-4 of Fig. 3; and

Fig. 5 is a perspective view of the improved cylindric valve member.

In the accompanying drawing, I have shown the valve member of myinvention embodied in a portable pneumatic chipping hammer wherein I isthe tool barrel and 2 is the cylinder which the barrel provides for thereciprocable hammering piston 3. A chisel 4 extends into the cylinder 2at the front end of the barrel through a supporting bushing 5 to receivethe power blows of the piston in the operation of the tool.

A handle member 6 is secured to the rear end of the barrel through atubular extension 'I on the handle member fitting over and having ascrew threaded connection with the barrel as shown herein. The handlemember 6 closes the rear end of the barrel and clamps a valve block 8therein. A pressure iiuid, such as compressed air, is supplied to thebarrel through a main supply passage 9 contained Within the handlemember and opening into the barrel over the valve block asshown. Thehandle member 6 carries a fitting IIJ at the outer'end of the passage 9for connection with an air supply hose (not shown). A manually operablethrottle valve, also not shown, is mounted Within the handle member forcontrolling the flow of live air to the tool cylinder 2. Said throttleValve has an actuating lever iI accessible at the handle as in thesepneumatic tools.

The valve block `8 is located at the rear endA of the barrel I within arecess I2 therein and is clamped by the handle member `Ii when screwedonto the barrel against a seat I3 which the barrel provides at the baseof said recess. The block 8 is provided with a bore I4 extendingdiametrically therethrough to mount a hollow cylindric distributingValve member I5 constructed in accordance with my present invention.

The valve block 8 has a snug iit within the recess I2, the contactingsurfaces of the parts having a ground iit to avoid air leakage. v

The block 8 closes the rear end of the cylinder 2 and the bore I4 isclosed at its opposite ends by plugs I6, Il which engage' thesurrounding wall of the recess I2 to hold the valve member i5 in placewithin the bore I4. The valve member I5 extends axially ofthe bore I4between the plugs and has sliding contact at its ends with the plugs.One of the plugs engages a key-way in the recess I2 to hold the blockfrom turning for the purpose disclosed in my said co-pendingapplication.

The block 8 has ports I8, I9 at the opposite sides of the valve memberI5 and these ports respectively connect the bore I4 to the opposite endsof the cylinder 2. The bore I4 at the ports I8, I9 is laterally Widerthan the diameter of the valve member I5 whereby the air pressuresupplied to the tool will .automatically shift the valve memberlaterally to alternately open and close said ports. The bore I4 at theseports is provided with arcuate valve seats 20, 2| on the same radius asthe valve member to close the ports when the valve member contacts theseseats. Between-the seats', the bore I4 has valve supports 22, 23 in theform of substantially straight surfaces tangential to the valve memberto support the same for lateral and revoluble shifting. The valve seatsand the valve supports have a ground nish similar to that of the valvemember, the block bein-g made of a heat treated alloy steel.

'The distance the valve member travels in lateral shifting is only asmall fraction of the radius of the valve member I5. This is due to thefact that the bore between the valve seats 20, 2I isv only slightlywider than the diameter of the valve member. Hence, the valve member Iis required to make only an extremely small lateral stroke to open andclose the ports I8, I9 resulting in a quick acting tool.

'Ihe valve member I5 is hollow as before stated and in accordance withmy invention is comprised of an outer cylindric shell portion 24 and aninner cylindric liner portion 25. The outer shell portion is made of aheat treated alloy steel or other hard metal to take a high finish bygrinding and to resist wear on the valve member in its lateral andrevoluble shifting within the bore. The inner liner portion 25 is madeof aluminum or other soft material and has a lpressed t within the outershell 24 to absorb the shocks to which the valve member is subjected inthe operation of the tool. These shocks result from the impacts of thevalve member with the valve seats 2B, 2I in the lateral shifting of thevalve member in response to the air pressure thereon and jars of thevalve member between the valve supports 22, 23 and against the end plugsI6, I'I from the more or less severe vibrations set up from the powerblows of the piston 3 on the chisel 4. 4While the distance between thevalve supports conforms substantially to the diameter of the valvemember and the length of the valve member accords with the spacingbetween the plugs, yet in practice there must be sufficient clearancesprovided between the partsfor a quick and rapid valve action whichresults in the valve member being subject to these tool vibrations. Withthe soft inner portion 25 of the valve member absorbing these shocks lthe outer shell 24 of the valve member is prevented from being crackedand the life of the valve member is materially prolonged.

As in my co-pending application and as shown herein, the valve block 8has inlet ports 2E, 21 leading from the upper surface of the block tothe upper part of the bore I4. The inlet ports convey air pressure fromthe handle member 5 to the bore, the latter having a pair of upperchannels 28, 29 to which the inlet ports are respectively connected. Theblock 8 has a pair of lower channels 30, 3I which supply live air to theunderside of the valve member. The channels 20 to 3| are located onopposite sides of the valve axis and are disposed between the valveseats and the valve supports, respectively, to supply air pressure tothe bore in any shifted position of the valve member.

The channels 23 to 3| extend longitudinally of the bore I4 for thegreater portion of the length of the valve member I5 and occupy thegreater portion of the circumference of the bore between the valve seatsand the valve supports to provide relatively large channels for a largeflow of air pressure to the cylinder at the instant of shifting of thevalve member to open a port. This results in instantaneous starting ofthe tool when held in any position. The ports I8, I9 are elongatedlongitudinally of the bore I4 to convey the large air ow to the cylinderas shown in Fie'. 3.

To reciprocate the piston 3 within the cylinder 2, the barrel I isprovided with longitudinally extending passages 32, 33, the formerconnecting the block port I8 and opening into the front end of thecylinder 2 through a port 34. 'I'he passages 33 are closed at theirinner ends by the valve block 8 and open into the cylinder 2 at twopoints in its length through ports 35, 36.

In operation, when the parts are in the positions shown in Figs. 1 and4, the valve member I5 closes the port I8 and opens the port I9. Liveair now enters the rear end of the cylinder 2 and the piston 3 is drivenforward on its power stroke. The front end of the cylinder is at thistime connected by the port 35 to the exhaust port 3'I in the barrel I.As soon as the piston uncovers the upper or rear port 36 the rear end ofthe cylinder 2 is opened to the exhaust. By this time the forward end ofthe piston 3 has closed the port 35 and the air entrapped between thepiston and the front end of the cylinder is compressed by the -pistcnand forced into the passages 32 to unseat the valve member I5 and shiftit towards the valve seat 2|. This shifting movement is aided by thelive air pressure on the valve member and the latter closes the port I9.This opens the port I8 and live air is admitted to the front end of thecylinder to force the piston 3 on its return stroke. As soon as thepiston uncovers the port 35 the front end of the cylinder is connectedto the exhaust whereupon the piston closes the port 38 and the airentrapped between the rearwardly moving piston and the rear end of thecylinder is compressed and the valve member is shifted into closingrelation with the port I8 to repeat the reciprocation of the piston.

The details of construction and arrangement of parts shown and describedmay be variously changed and modified without departing from the spiritand scope of my invention, except as pointed out inthe annexed claim.

I claim as my invention:

In a portable pneumatic hammer, a barrel providing a cylinder andadapted to support a chisel or like tool at the forward end of thebarrel, a piston reciprocable within the cylinder for de liverlng hammerblows on the chisel, a valve block clamped to the barrel at the rear endof the cylinder and having a bore, said block having inlet ports forsupplying pressure fluid to the bore and service ports for connectingthe bore to the opposite ends of the cylinder, and a hollow cylindricaldistributing valve member located within the bore and shiftablelaterally thereof by the pressure uid supplied to the cylinder throughthe bore, said valve member in shifting having contact with the block atthe service ports for alternately opening and closing the same toreciprocate the piston within the cylinder, said valve member beingcomprised of a relatively thin outer cylindrical shell of hard metal andan inner cylindrical liner of a softer, bulkier, lighter, deadeningmaterial, said liner being substantially equal in length to the outershell and having a tight nt within and supported by the shell to absorbthe impacts of the shell with the block in the shifting of the valvemember and from the jars of the valve member against the block from thevibrations set up in the barrel from the hammer blows of the piston onthe chisel to prevent cracking of the shell and to reduce the thicknessof the same to lighten the valve member for a rapid lateral shiftingmovement.

FRI'I'HIOF P. FORSS.

